Preclinical Research & Development Current drugs for obesity treatment have limited efficacy and considerable adverse effects. Combination of drugs with complementary mechanisms of action at lower doses may produce a greater efficacy with a better safety profile. This study was designed to assess the anorectic effect and safety of a diethylpropion + topiramate mixture in rats. The anorectic effect of drugs was measured using a sweetened milk consumption model, and the corresponding interaction was determined by isobolographic analysis, interaction index and confidence intervals. Additionally, blood pressure was measured using a sphygmomanometer in the rat tail. Diethylpropion and topiramate alone or in combination increased the anorectic effect in a dose-dependent fashion in either nondeprived or 12 hr food-deprived rats. All theoretical ED values of diethylpropion + topiramate combinations at 1:1, 1:3, and 3:1 dose ratios were significantly higher than experimental ED values. In addition, interaction indices and confidence intervals confirmed the potentiation between both drugs. Theoretical ED of diethylpropion + topiramate combination did not affect the blood pressure. Data suggests that low doses of the diethylpropion + topiramate combination can potentiate the anorectic effect of individual drugs with a better safety profile, which deserves further investigation in clinical trials.